Uh, what about solar activity? Seems to not have been considered.
"The factually observed solar activity, and it's impact on earth's global temperature is considered when they "adjust" the global mean temperatures in order to analyze trends."
WTH?, you ask. This was an answer I got from a Liberal PHD and avowed MMGW worshiper to your question. Let me try to explain what he tried to sell me. Since our Sun is in a cooling cycle with less radiation activity, it affects the global temperature. So to account for that affect, they add a "correction factor" to the global temperatures in order to maintain a constant when they run the models. I laughed in his face of course and asked how taking the source of temperature out of the global temperature equation makes any sense.
I am pretty sure he was making it up as he went along. But it would not completely surprise me if there was any truth. Think about their logic. This started when I showed him data that the earth had not "warmed" over the last 20 years and he suggested it was because of solar cycles. I thought I was on candid camera.